This invention relates generally to medical treatment apparatus and methods. More specifically, it is concerned with apparatus and methods for use in sustaining vitality of an organ in the gastrointestinal tract by catheterization. The several aspects of the invention include improvements in catheter placement, ischemia detection, and oxygenation.
The nature of human anatomy is such that each individual organ's vitality is sustained by the circulation of blood through the organ's vascular system. Each organ's vascular system is of course a part of the body's larger cardio-vascular system.
For any of various reasons the circulation, and hence oxygen delivery, to any given organ may become insufficient to sustain the full vitality of that organ. For example, partial occlusion of an artery may reduce blood flow to a point where the oxygen supply is insufficient. An occlusion, whether full or partial, may be due entirely to naturally occurring phenomenon or it may be in consequence of certain procedures. Regardless of the cause, reduced oxygen delivery can have potentially devastating effects on a patient.
As another example, surgical procedures, possibly not even directly related to a particular organ, may have an effect on the organ. For instance, in the case of certain vascular surgery procedures, it may be necessary to interrupt the blood flow to a given organ or organs during the course of procedures. External blood pumps may be used to supply the organ or organs during these procedures or else the procedures must be performed with sufficient rapidity that the temporary interruption of circulation to an organ will not produce grave consequences.
The present invention is in one respect directed to novel apparatus and methods for sustaining vitality of an internal organ in situations such as these, particularly with reference to gastrointestinal organs. With the present invention it is unnecessary to utilize external devices, such as blood pumps, in association with the vascular system. The present invention provides apparatus and methods which can be used at any desired time, for example, pre-operatively, during an operation, or post-operatively.
One important advantage over prior methods and apparatus is that the invention does not directly involve the cardiovascular system. Rather, the invention contemplates the introduction of a catheter into an organ of interest. A disclosed embodiment of catheter comprises a tube having a walled chamber structure at one end. The catheter is introduced to dispose the chamber structure against the lumen of the organ of interest. The material of the chamber is one which is freely permeable to gas but poorly permeable to liquid. The tube contains a conduit for delivering fluid to the chamber.
The catheter has a dual capability, one, to monitor incipient ischemia in the organ of interest, and two to oxygenate the organ. When the organ is being monitored for ischemia, perfusion fluid is introduced and subsequently extracted to obtain a CO.sub.2 sample from the lumen of the organ. The pCO.sub.2 measurement is utilized to calculate the organ's pH. The calculated pH can be used as an indicator of incipient ischemia.
When the catheter is being used for organ oxygenation, oxygen is perfused through the chamber via the tube from an external source. The external source may comprise any suitable means to create an oxygen partial pressure gradient between the interior of the chamber and the lumen of the organ whereby oxygen can diffuse through the wall of the chamber and into the organ. Carbon dioxide gas generated by the organ can also diffuse through the wall of the chamber to be conveyed back through the tube for removal.
In the disclosed embodiment, the chamber and tube are so constructed and arranged as to create an axial flow along the interior of the wall of the chamber along substantially the full length of the chamber. This promotes the maximum area availability for delivering oxygen to an organ, particularly in the case where the organ is in the gastrointestinal tract. The diameter of the chamber is less than that of the organ so that the catheter does not block passage through the organ. The invention also contemplates the use of agents such as the use of vasodialator to enhance oxygenation locally and the use of blood and/or blood substitutes for oxygen-bearing purposes.
The invention also provides for improved catheter placement through the use of an auxiliary placement device in association with the catheter. An endoscope may be used as the auxiliary placement device. A disclosed embodiment of catheter has magnetically responsive structure at its tip, and the auxiliary device has an electromagnet which is cooperatively associated with the magnetic tip. The auxiliary device is operated to maintain electro-magnetic attraction of the magnetic tip structure during an initial phase of the placement process. The auxiliary device is relatively stiffer than the catheter and is used to force the catheter tip past the pylorus when the catheter is introduced into the intestines from the stomach. Thereafter a separate external magnet is used to attract the catheter tip, the electro-magnet is de-energized, and the auxiliary device withdrawn. Final placement of the catheter is attained through manipulation of the external magnet.
The foregoing features, advantages and benefits of the invention, along with additional ones, will be seen in the ensuing description and claims which should be considered in conjunction with the accompanying drawings. The drawings disclose a preferred embodiment of the invention according to the best mode contemplated at the present time in carrying out the invention.